1. Field of the Invention
The invention relates to a method for identifying a sound signal which characteristic values are derived from a time-limited portion of said sound signal, specifically a speech signal, the sound signal being divided into adjacent frequency ranges and the sound signal of each frequency range being integrated to short-time-spectrum signals over consecutive equal time intervals. The invention also relates to an arrangement for carrying out the method.
2. Description of the Prior Art
Methods of the aforementioned type serve for identifying or allocating sound signals, which are not identically reproducible, with the aid of the characteristic values. Such sound signals may for example be produced by machines during normal operation or when these machines are tested, in which case a change, which may be indicative of possible failure of the machine is to be detected at the earliest possible stage. Another significant type of sound signals are speech signals by means of which a speaker is to be identified. Such sound signals have the property that they are generally not exactly reproducible and, moreover contain a very large amount of information, so that a direct storage for comparison is impracticable. It is therefore necessary to reduce this amount of information substantially by deriving characteristic values from said signals. Suitably, these characteristic values should only contain that amount of information which is necessary to characterize the relevant sound signal.
It is known to derive consecutive short-time spectra from a sound signal by integration of the energy of the sound signal in adjacent frequency ranges. The long-time spectrum can be derived from said short-time spectrum by forming their sum and, moreover, the standard deviations for the individual frequency ranges can be derived from the long-time spectrum and the short-time spectra. The values of the long-term spectrum or of the standard deviations then represent the characteristic values of the sound signal or the speech signal. However, these known methods frequently result in an excessive reduction of the information content, so that a satisfactory discrimination of similar sound signals or speech signals is not possible.